What you'll need:
- Water
- A large bowl with a lip around the top (a smaller bowl or cup will work too)
- A strip of material or cloth
- Soapy mixture for making bubbles (water and some dishwashing liquid should do the trick)
- Dry ice - one piece for a cup, more for a bowl. Places where adults can buy dry ice include large grocery stores and Walmart. Butchers and ice cream stores might have some too.
Safety first! Be careful with dry ice as it can cause skin damage if not used safely. Adults should handle dry ice with gloves and avoid directly breathing in the vapor.
Instructions:
- Place your dry ice in the bowl and add some water (it should start looking like a spooky cauldron).
- Soak the material in your soapy mixture and run it around the lip of the bowl before dragging it across the top of the bowl to form a bubble layer over the dry ice.
- Stand back and watch your bubble grow!
What's happening?
Dry ice is carbon dioxide (CO2) in its solid form. At temperatures above -56.4 °C (-69.5 °F), dry ice changes directly from a solid to a gas, without ever being a liquid. This process is called sublimation. When dry ice is put in water it accelerates the sublimation process, creating clouds of fog that fill up your dry ice bubble until the pressure becomes too much and the bubble explodes, spilling fog over the edge of the bowl. Dry ice is sometimes used as part of theater productions and performances to create a dense foggy effect. It is also used to preserve food, freeze lab samples and even to make ice cream!
